The last fifteen years has seen widespread adaptation of cellular telephony systems for wireless wide area networks (WWANs). At present there are believed to be over two billion cellular telephone users globally. Countries, or in some cases supra-national groupings, regulate electromagnetic spectrum usage independently of each other. This means that cellular networks in different parts of the world do not necessarily use the same frequencies. Additionally, competition between different corporations, and in some cases industry groups, have produced different cellular telephony communication protocols such as GSM, CDMA, WCDMA, and iDEN. In some cases, a particular protocol may be used within different carrier frequency bands in different countries. Some cellular telephone handsets (cell phones) are cable of operating in multiple frequency bands for use in different countries.
Furthermore, it is anticipated that more wireless devices that support multiple competing cellular telephony protocols will be developed. To make these wireless communication devices even more useful, manufacturers have added the ability to communicate using one or more shorter-range wireless communication protocols such as WiFi for wireless local area networks (WLANs), WiMax for wireless metropolitan area networks (WMANs), or Bluetooth for wireless personal area networks (WPANs).
A wireless communication device is, of course, meant to be mobile. By design, a wireless communication device's receiver frequently scans for base station signals in its vicinity so that, when a user moves from one cell's coverage to another, the communications link can be handed off seamlessly. Additionally, a user may move out of a zone of service using one RAT into a zone covered using a second RAT, for example an area still using a legacy protocol, and need to scan a large amount of spectrum to find a compatible network. In a similar case, a cell phone may be activated after a user has deplaned in a foreign country, in which case the cell phone methodically scans all frequencies for any RAT it is capable of using. Wireless mobile communication devices may also automatically scan for shorter range communication signals as well as WWAN signals (or instead of WWAN signals). All of the scanning activities occur even if the cell phone is in idle mode (e.g., not in a call), keeping the cell phone's receiver busy, and draining precious battery power. Given the inconvenience of reduced battery life and the increased awareness of the need to conserve energy globally, it would be desirable to be able to reduce the power consumed by scanning activities.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.